An In Vivo Assessment of Regional Brain Temperature during Whole-Body Cooling for Neonatal Encephalopathy

Objective To assess differences in regional brain temperatures during whole-body hypothermia and test the hypothesis that brain temperature profile is nonhomogenous in infants with hypoxic–ischemic encephalopathy. Study design Infants with hypoxic–ischemic encephalopathy were enrolled prospectively in this observational study. Magnetic resonance (MR) spectra of basal ganglia, thalamus, cortical gray matter, and white matter (WM) were acquired during therapeutic hypothermia. Regional brain tissue temperatures were calculated from the chemical shift difference between water signal and metabolites in the MR spectra after performing calibration measurements. Overall difference in regional temperature was analyzed by mixed-effects model; temperature among different patterns and severity of injury on MR imaging also was analyzed. Correlation between temperature and depth of brain structure was analyzed using repeated-measures correlation. Results In total, 53 infants were enrolled (31 girls, mean gestational age: 38.6 ± 2 weeks; mean birth weight: 3243 ± 613 g). MR spectroscopy was acquired at mean age of 2.2 ± 0.6 days. A total of 201 MR spectra were included in the analysis. The thalamus, the deepest structure (36.4 ± 2.3 mm from skull surface), was lowest in temperature (33.2 ± 0.8°C, compared with basal ganglia: 33.5 ± 0.9°C; gray matter: 33.6 ± 0.7°C; WM: 33.8 ± 0.9°C, all P Conclusions Whole-body hypothermia was effective in cooling deep brain structures, whereas superficial structures were warmer, with temperatures significantly greater than rectal temperatures.